the following description is of the best - contemplated mode of carrying out the disclosure . this description is made for the purpose of illustrating the general principles of the disclosure and should not be taken in a limiting sense . the scope of the disclosure is best determined by reference to the appended claims . the disclosure provides an organometallic compound having a structure represented by formula ( i ) or ( ii ): in formula ( i ) and ( ii ), r 1 , r 2 may be hydrogen , phenyl , biphenyl , diisopropyl amino , or derivatives thereof . the organometallic compounds according to formula ( i ) or ( ii ) of the disclosure include the following compounds , as shown in table 1 . in addition , the contraction thereof are also named and shown in table 1 . fig1 shows a cross - sectional view of an embodiment of an organic electroluminescent device 10 . the organic electroluminescent device 10 includes a substrate 12 , a bottom electrode 14 , an electroluminescent element 16 , and a top electrode 18 , as shown in fig1 . the organic electroluminescent device may be top - emission , bottom - emission , or dual - emission organic electroluminescent device . the substrate 12 may be a glass , plastic , or semiconductor substrate . suitable materials for the bottom electrode 14 and the top electrode 18 may be li , mg , ca , al , ag , in , au , w , ni , pt , cu , indium tin oxide ( ito ), indium zinc oxide ( izo ), aluminum zinc oxide ( azo ), zinc oxide ( zno ) or combinations thereof , formed by thermal evaporation , sputtering , or plasma enhanced chemical vapor deposition . furthermore , at least one of the bottom electrode 14 and the top electrode 18 is transparent . the electroluminescent element 16 includes at least one emission layer , and may further include a hole injection layer , a hole transport layer , an electron transport layer , an electron injection layer or other layers . specifically , in accordance with an embodiment of the disclosure , the electroluminescent element 16 includes organometallic compounds having formula ( i ) or ( ii ). that is , in the electroluminescent element 16 , at least one layer includes the aforementioned organometallic compounds . according to another embodiment of the disclosure , the organic electroluminescent device 10 may be a phosphorescent organic electroluminescent device , and the phosphorescent electroluminescent element includes a host material and a phosphorescent dopant material . the phosphorescent dopant material includes the aforementioned organometallic compounds having formula ( i ) or ( ii ). one of ordinary skill in the art may dope the required phosphorescent dopant materials with the disclosed organometallic compounds and alter the doping amount of the adopted dopants based on the used organic electroluminescent material and the required characteristics of the device . therefore , the doping amount of the dopants is neither related to the characteristic of the invention nor the base of limiting the scope of the invention . for instance , while adopting the organometallic compound having formula ( i ) as a dopant in the emission layer , the doping amount of the organometallic compound having formula ( i ) may be between 0 . 1 % to 15 % based on the weight of the host material . one of ordinary skill in the art may dope the disclosed organometallic compounds with the required phosphorescent dopant materials and alter the doping amount of the adopted dopants based on the used organic electroluminescent material and the required characteristics of the device . therefore , the doping amount of the dopants is neither related to the characteristic of the invention nor the base of limiting the scope of the invention . in order to clearly disclose the organic electroluminescent devices of the disclosure , the following examples ( employing the organometallic compounds of example 1 serving as dopant ) are intended to illustrate the disclosure more fully without limiting their scope , since numerous modifications and variations will be apparent to those skilled in this art . compound ( 2 ) ( 4 - phenyl benzoyl chloride , 25 g , 115 . 47 mmol ) and 150 ml h 2 o were added into a 500 ml single - neck bottle with an addition funnel . next , compound ( 1 ) ( 2 -( 2 - aminoethyl ) thiophene , 17 . 63 g , 138 . 56 mmol , 1 . 2 eq .) was added dropwisely into the bottle via the addition funnel under ice - bath cooling . white solid was gradually formed . after dropping , a naoh aqueous solution ( 20 %) was added into the bottle and stirred overnight . after filtration with a porcelain funnel , a white solid of compound ( 3 ) ( 36 g , yield of 100 %) was obtained . compound ( 3 ) was analyzed by nmr spectroscopy . the spectral information of compound ( 3 ) is listed below : 1 h nmr ( cdcl 3 , 200 mhz ) δ 7 . 79 ( d , j = 2 . 0 hz , 2h ), 7 . 62 ( t , j = 6 . 8 , 1 . 8 hz , 4h ), 7 . 38 - 7 . 58 ( m , 3h ), 7 . 20 ( dd , j = 5 . 2 , 1 . 2 hz , 1h ), 7 . 00 ( d , j = 2 . 0 hz , 1h ), 6 . 99 ( s , 1h ), 6 . 37 ( s , 1h ), 3 . 76 ( q , j = 6 . 6 , 6 . 2 hz , 2h ), 3 . 19 ( t , j = 6 . 2 hz , 2h ). compound ( 3 ) ( 12 g , 39 mmol ) and toluene ( 175 ml ) were added into a 250 ml single - neck round - bottom flask . pocl 3 ( 10 . 9 ml , 117 mmol , 3 eq .) was added dropwisely into the flask via an addition funnel under ice - bath cooling . after dropping , the ice - bath was replaced by an oil bath and heated until toluene reflux . after reaction overnight , a saturated nahco 3 aqueous solution was added into the flask for neutralization of the reaction . after toluene extraction , a toluene solution was collected and dried by dried magnesium sulfate . after evaporation and standing for several hours , compound ( 4 ) ( crystal , 6 . 7 g ) was obtained with a yield of 60 %. compound ( 4 ) was analyzed by nmr spectroscopy . the spectral information of compound ( 4 ) is listed below : 1 h nmr ( cdcl 3 , 200 mhz ) δ 7 . 79 ( d , j = 2 . 0 hz , 2h ), 7 . 66 - 7 . 75 ( m , 4h ), 7 . 37 - 7 . 50 ( m , 3h ), 7 . 10 ( q , j = 5 . 2 , 2 . 8 hz , 2h ), 3 . 98 ( t , j = 8 . 4 hz , 2h ), 2 . 95 ( t , j = 7 . 6 hz , 2h ). compound ( 4 ) ( 6 . 7 g , 23 . 2 mmol ), toluene ( 100 ml ) and 10 % pd / c ( 10 g ) were added into a 250 ml single - neck round - bottom flask and heated to toluene reflux . after reaction for 48 hrs , the result was filtrated by diatomaceous earth ( celite 545 ) to remove pd / c . after the filtrate was concentrated and purified by column chromatography ( ethyl acetate / n - hexane = 1 / 5 ), a pale khaki solid of compound ( 5 ) ( 5 g ) was obtained with a yield of 75 %. compound ( 5 ) was analyzed by nmr spectroscopy . the spectral information of compound ( 5 ) is listed below : 1 h nmr ( cdcl 3 , 200 mhz ) δ 8 . 57 ( d , j = 5 . 8 hz , 1h ), 7 . 94 ( d , j = 8 . 4 hz , 2h ), 7 . 67 - 7 . 82 ( m , 6h ), 7 . 38 - 7 . 54 ( m , 4h ). compound ( 5 ) ( 5 . 0 g , 17 . 4 mmol , 2 . 2 eq . ), ircl 3 xh 2 o ( 2 . 36 g , 7 . 9 mmol ), 2 - methoxy ethanol ( 21 ml ), and water ( 7 ml ) were added into a 100 ml single - neck round - bottom flask . after heating to 140 ° c . and reacting for 24 hrs , the reaction was quenched by adding plenty of water . after filtration , compound ( 6 ) ( orange solid , 5 . 5 g ) was obtained with a yield of 44 %. compound ( 6 ) was analyzed by nmr spectroscopy . the spectral information of compound ( 6 ) is listed below : 1 h nmr ( cdcl 3 , 200 mhz ) δ 9 . 19 ( d , j = 6 . 6 hz , 4h ), 8 . 38 ( d , j = 6 . 0 hz , 4h ), 8 . 13 ( d , j = 8 . 4 hz , 4h ), 7 . 77 ( d , j = 5 . 8 hz , 4h ), 7 . 08 - 8 . 20 ( m , 24h ), 7 . 01 ( d , j = 6 . 6 , 4h ), 6 . 27 ( d , j = 1 . 8 hz , 4h ). compound ( 6 ) ( 5 . 0 g , 3 . 13 mmol ), compound ( 7 ) ( 2 , 4 - pentanedione , 1 . 25 g , 12 . 52 mmol , 4 eq . ), na 2 co 3 ( 1 . 33 g , 12 . 52 mmol , 4 eq . ), and 2 - methoxyethanol ( 30 ml ) were added into a 100 ml single - neck round - bottom flask and heated to 140 ° c . after reacting for 24 hrs and cooling to room temperature , the result was washed with 50 ml water and filtered to obtain orange solid product . the product was purified by column chromatography with dichloromethane / n - hexane ( 1 / 1 ), obtaining compound ( po - 01 - bp ) ( orange solid powder , 1 . 35 g ) with a yield of 50 %. compound ( po - 01 - bp ) was analyzed by nmr spectroscopy . the spectral information of compound ( po - 01 - bp ) is listed below : 1 h nmr ( 200 mhz , cdcl 3 ) δ 8 . 50 ( d , j = 6 . 2 hz , 2h ), 8 . 37 ( d , j = 5 . 6 hz , 2h ), 8 . 17 ( d , j = 8 . 0 hz , 2h ), 7 . 66 - 7 . 71 ( m , 4h ), 7 . 01 - 7 . 22 ( m , 12h ), 6 . 56 ( d , j = 2 . 0 hz , 2h ), 5 . 23 ( s , 1h ), 1 . 79 ( s , 6h ). compound ( 8 ) ( bromobenzene , 1 . 45 ml , 13 . 76 mmol ) and distilled thf ( 50 ml , anhydrous ) were added into a 250 ml dual - neck round - bottom flask . after cooling to − 78 ° c ., n - buli ( 8 . 6 ml , 13 . 76 mmol ) was added dropwisely into the flask . after dropping and stirring for 30 minutes , n , n - diisopropylcarbodiimide ( 2 . 15 ml , 13 . 76 mmol ) was added dropwisely into the flask under − 78 ° c . after dropping and rapid stirring for 30 minutes , a solution containing compound ( 9 ) was obtained . the solution containing compound ( 9 ) was dropped into a thf solution ( 70 ml ) containing compound ( 6 ) ( 5 . 5 g , 3 . 44 mmol ) and heated to reflux . after reaction overnight and removal of solvent , the result was purified by column chromatography with ethyl acetate / n - hexane ( 1 / 1 ), obtaining compound ( po - 01 - bp - dipba ) ( dark red solid , 1 . 2 g ) with a yield of 36 %. compound ( po - 01 - bp - dipba ) was analyzed by nmr spectroscopy . the spectral information of compound ( po - 01 - bp - dipba ) is listed below : 1 h nmr ( 200 mhz , cdcl 3 ) δ 9 . 43 ( d , j = 6 . 4 hz , 2h ), 8 . 38 ( d , j = 6 . 0 hz , 2h ), 8 . 17 ( d , j = 8 . 0 hz , 2h ), 7 . 79 ( d , j = 6 . 6 hz , 2h ), 7 . 70 ( d , j = 5 . 6 hz , 2h ), 7 . 05 - 7 . 44 ( m , 17h ), 6 . 58 ( d , j = 1 . 8 , 2h ), 3 . 26 ( m , 2h ), 0 . 72 ( d , j = 6 . 2 hz , 6h ), − 0 . 09 ( d , j = 6 . 2 hz , 6h ). compound ( 10 ) ( diisopropylamine , 1 . 87 ml , 13 . 24 mmol ) and distilled thf ( 50 ml , anhydrous ) were added into a 250 ml dual - neck round - bottom flask . after cooling to − 78 ° c ., n - buli ( 8 . 3 ml , 13 . 24 mmol ) was added dropwisely into the flask . after dropping and stirring for 30 minutes , n , n - diisopropylcarbodiimide ( 2 . 1 ml , 13 . 24 mmol ) was added dropwisely into the flask under − 78 ° c . after dropping and rapid stirring for 30 minutes , a solution containing compound ( 11 ) was obtained . the solution containing compound ( 11 ) was dropped into a thf solution ( 70 ml ) containing compound ( 6 ) ( 5 . 3 g , 3 . 31 mmol ) and heated to reflux . after reaction overnight and removal of solvent , the result was purified by column chromatography with ethyl acetate / n - hexane ( 1 / 1 ), obtaining compound ( po - 01 - bp - dipig ) ( dark red solid , 1 . 28 g ) with a yield of 40 %. compound ( po - 01 - bp - dipig ) was analyzed by nmr spectroscopy . the spectral information of compound ( po - 01 - bp - dipig ) is listed below : 1 h nmr ( 200 mhz , cdcl 3 ) δ 9 . 23 ( d , j = 6 . 2 hz , 2h ), 8 . 20 ( d , j = 5 . 8 hz , 2h ), 8 . 14 ( d , j = 7 . 6 hz , 2h ), 7 . 60 ( d , j = 6 . 6 hz , 2h ), 7 . 45 ( d , j = 5 . 6 hz , 2h ), 7 . 05 - 7 . 40 ( m , 12h ), 6 . 48 ( s , 2h ), 3 . 81 ( m , 2h ), 3 . 54 ( m , 2h ), 1 . 23 ( t , j = 5 . 0 hz , 12h ), 0 . 83 ( d , j = 6 . 2 hz , 6h ), − 0 . 05 ( d , j = 5 . 8 hz , 6h ). a glass substrate with a patterned indium tin oxide ( ito ) film of 150 nm was provided and then washed with a neutral cleaning agent , acetone , and ethanol with ultrasonic agitation . after drying the substrate with a nitrogen flow , the substrate was subjected to a uv / ozone treatment for 30 minutes . next , pedot ( poly ( 3 , 4 )- ethylendioxythiophen ) and pss ( e - polystyrenesulfonate ) were selected to coat on the ito film by a spin coating process ( with a rotation rate of 2 , 000 rpm ) to form a pedot : pss film ( with a thickness of 45 nm , serving as a hole injection layer ). after heating to 130 ° c . for 10 min , a tapc ( di -[ 4 -( n , n - ditolyl - amino )- phenyl ] cyclohexane ) layer ( with a thickness of 35 nm ), a tcta ( 4 , 4 ′, 4 ″- tris ( carbazol - 9 - yl ) triphenylamine ) layer doped with compound ( po - 01 - bp ) ( the ratio between tcta and compound ( po - 01 - bp ) was 100 : 6 , with a thickness of 10 nm ), a tmpypb ( 1 , 3 , 5 - tri [( 3 - pyridyl )- phen - 3 - yl ] benzene ) layer ( with a thickness of 42 nm ), a lif layer ( with a thickness of 0 . 5 nm ), and an al layer ( with a thickness of 120 nm ) were subsequently deposited on the ito film under 10 − 6 torr and packaged , obtaining the organic electroluminescent device ( 1 ). the structure of the organic electroluminescent device ( 1 ) is described in the following : ito ( 150 nm )/ tapc ( 35 nm )/ tcta : compound ( po - 01 - bp ) ( 6 %, 10 nm )/ tmpypb ( 42 nm )/ lif ( 0 . 5 nm )/ al ( 120 nm ) the optical properties including brightness ( cd / m 2 ), current efficiency ( cd / a ), power efficiency ( 1 m / w ), emission wavelength ( nm ), and color coordinates ( x , y ) of the organic electroluminescent device ( 1 ) were measured and the results are described in table 2 . a glass substrate with a patterned indium tin oxide ( ito ) film of 150 nm was provided and then washed with a neutral cleaning agent , acetone , and ethanol with ultrasonic agitation . after drying the substrate with a nitrogen flow , the substrate was subjected to a uv / ozone treatment for 30 minutes . next , pedot ( poly ( 3 , 4 )- ethylendioxythiophen ) and pss ( e - polystyrenesulfonate ) were selected to coat on the ito film by a spin coating process ( with a rotation rate of 2 , 000 rpm ) to form a pedot : pss film ( with a thickness of 45 nm , serving as a hole injection layer ). after heating to 130 ° c . for 10 min , a tapc ( di -[ 4 -( n , n - ditolyl - amino )- phenyl ] cyclohexane ) layer ( with a thickness of 35 nm ), a tcta ( 4 , 4 ′, 4 ″- tris ( carbazol - 9 - yl ) triphenylamine ) layer doped with compound ( po - 01 - bp - dipba ) ( the ratio between tcta and compound ( po - 01 - bp - dipba ) was 100 : 6 , with a thickness of 10 nm ), a tmpypb ( 1 , 3 , 5 - tri [( 3 - pyridyl )- phen - 3 - yl ] benzene ) layer ( with a thickness of 42 nm ), a lif layer ( with a thickness of 0 . 5 nm ), and an al layer ( with a thickness of 120 nm ) were subsequently deposited on the ito film under 10 − 6 torr and packaged , obtaining the organic electroluminescent device ( 2 ). the structure of the organic electroluminescent device ( 2 ) is described in the following : ito ( 150 nm )/ tapc ( 35 nm )/ tcta : compound ( po - 01 - bp - dipba ) ( 6 %, 10 nm )/ tmpypb ( 42 nm )/ lif ( 0 . 5 nm )/ a1 ( 120 nm ) the optical properties including brightness ( cd / m 2 ), current efficiency ( cd / a ), power efficiency ( 1 m / w ), emission wavelength ( nm ), and color coordinates ( x , y ) of the organic electroluminescent device ( 2 ) were measured and the results are described in table 2 . a glass substrate with a patterned indium tin oxide ( ito ) film of 150 nm was provided and then washed with a neutral cleaning agent , acetone , and ethanol with ultrasonic agitation . after drying the substrate with a nitrogen flow , the substrate was subjected to a uv / ozone treatment for 30 minutes . next , pedot ( poly ( 3 , 4 )- ethylendioxythiophen ) and pss ( e - polystyrenesulfonate ) were selected to coat on the ito film by a spin coating process ( with a rotation rate of 2 , 000 rpm ) to form a pedot : pss film ( with a thickness of 45 nm , serving as a hole injection layer ). after heating to 130 ° c . for 10 min , a tapc ( di -[ 4 -( n , n - ditolyl - amino )- phenyl ] cyclohexane ) layer ( with a thickness of 35 nm ), a tcta ( 4 , 4 ′, 4 ″- tris ( carbazol - 9 - yl ) triphenylamine ) layer doped with compound ( po - 01 - bp - dipig ) ( the ratio between tcta and compound ( po - 01 - bp - dipig ) was 100 : 6 , with a thickness of 10 nm ), a tmpypb ( 1 , 3 , 5 - tri [( 3 - pyridyl )- phen - 3 - yl ] benzene ) layer ( with a thickness of 42 nm ), a lif layer ( with a thickness of 0 . 5 nm ), and an al layer ( with a thickness of 120 nm ) were subsequently deposited on the ito film under 10 − 6 torr and packaged , obtaining the organic electroluminescent device ( 3 ). the structure of the organic electroluminescent device ( 3 ) is described in the following : ito ( 150 nm )/ tapc ( 35 nm )/ tcta : compound ( po - 01 - bp - dipig ) ( 6 %, 10 nm )/ tmpypb ( 42 nm )/ lif ( 0 . 5 nm )/ al ( 120 nm ) the optical properties including brightness ( cd / m 2 ), current efficiency ( cd / a ), power efficiency ( 1 m / w ), emission wavelength ( nm ), and color coordinates ( x , y ) of the organic electroluminescent device ( 3 ) were measured and the results are described in table 2 . a glass substrate with a patterned indium tin oxide ( ito ) film of 150 nm was provided and then washed with a neutral cleaning agent , acetone , and ethanol with ultrasonic agitation . after drying the substrate with a nitrogen flow , the substrate was subjected to a uv / ozone treatment for 30 minutes . next , pedot ( poly ( 3 , 4 )- ethylendioxythiophen ) and pss ( e - polystyrenesulfonate ) were selected to coat on the ito film by a spin coating process ( with a rotation rate of 2 , 000 rpm ) to form a pedot : pss film ( with a thickness of 45 nm , serving as a hole injection layer ). after heating to 130 ° c . for 10 min , a light - emitting film ( with a thickness of 30 nm ) was formed on the pedot : pss film by a spin coating process . the composition of the light - emitting film included tcta ( 4 , 4 ′, 4 ″- tris ( carbazol - 9 - yl ) triphenylamine ) and compound ( po - 01 - bp ) tcta and compound ( po - 01 - bp ) ( the weight ratio between tcta and compound ( po - 01 - bp ) was 94 : 6 ) were dissolved in chlorobenzene to prepare the light - emitting film . next , a tmpypb ( 1 , 3 , 5 - tri [( 3 - pyridyl )- phen - 3 - yl ] benzene ) layer ( with a thickness of 55 nm , serving as a hole - block / electron - transport layer ) was deposited on the light - emitting film . next , a lif layer ( with a thickness of 1 nm ) and an al layer ( with a thickness of 100 nm ) were subsequently deposited on the tmpypb film and packaged , obtaining the organic electroluminescent device ( 4 ). the structure of the organic electroluminescent device ( 4 ) is described in the following : ito ( 150 nm )/ pedot : pss ( 45 nm )/ tcta : compound ( po - 01 - bp ) ( 30 nm )/ tmpypb ( 55 nm )/ lif ( 1 nm )/ a1 ( 100 nm ) the optical properties including brightness ( cd / m 2 ), current efficiency ( cd / a ), power efficiency ( 1 m / w ), emission wavelength ( nm ), and color coordinates ( x , y ) of the organic electroluminescent device ( 4 ) were measured and the results are described in table 2 . a glass substrate with a patterned indium tin oxide ( ito ) film of 150 nm was provided and then washed with a neutral cleaning agent , acetone , and ethanol with ultrasonic agitation . after drying the substrate with a nitrogen flow , the substrate was subjected to a uv / ozone treatment for 30 minutes . next , pedot ( poly ( 3 , 4 )- ethylendioxythiophen ) and pss ( e - polystyrenesulfonate ) were selected to coat on the ito film by a spin coating process ( with a rotation rate of 2 , 000 rpm ) to form a pedot : pss film ( with a thickness of 45 nm , serving as a hole injection layer ). after heating to 130 ° c . for 10 min , a light - emitting film ( with a thickness of 30 nm ) was formed on the pedot : pss film by a spin coating process . the composition of the light - emitting film included npb ( n , n ′- bis ( naphthalen - 1 - yl )- n , n ′- bis ( phenyl )- benzidine ) and compound ( po - 01 - bp - dipba ) npb and compound ( po - 01 - bp - dipba ) ( the weight ratio between npb and compound ( po - 01 - bp - dipba ) was 95 : 5 ) were dissolved in chlorobenzene to prepare the light - emitting film . next , a tmpypb ( 1 , 3 , 5 - tri [( 3 - pyridyl )- phen - 3 - yl ] benzene ) layer ( with a thickness of 55 nm , serving as a hole - block / electron - transport layer ) was deposited on the light - emitting film . next , a lif layer ( with a thickness of 1 nm ) and an al layer ( with a thickness of 100 nm ) were subsequently deposited on the tmpypb film and packaged , obtaining the organic electroluminescent device ( 5 ). the structure of the organic electroluminescent device ( 5 ) is described in the following : ito ( 150 nm )/ pedot : pss ( 45 nm )/ npb : compound ( po - 01 - bp - dipba ) ( 30 nm )/ tmpypb ( 55 nm )/ lif ( 1 nm )/ a1 ( 100 nm ) the optical properties including brightness ( cd / m 2 ), current efficiency ( cd / a ), power efficiency ( 1 m / w ), emission wavelength ( nm ), and color coordinates ( x , y ) of the organic electroluminescent device ( 5 ) were measured and the results are described in table 2 . a glass substrate with a patterned indium tin oxide ( ito ) film of 150 nm was provided and then washed with a neutral cleaning agent , acetone , and ethanol with ultrasonic agitation . after drying the substrate with a nitrogen flow , the substrate was subjected to a uv / ozone treatment for 30 minutes . next , pedot ( poly ( 3 , 4 )- ethylendioxythiophen ) and pss ( e - polystyrenesulfonate ) were selected to coat on the ito film by a spin coating process ( with a rotation rate of 2 , 000 rpm ) to form a pedot : pss film ( with a thickness of 45 nm , serving as a hole injection layer ). after heating to 130 ° c . for 10 min , a light - emitting film ( with a thickness of 30 nm ) was formed on the pedot : pss film by a spin coating process . the composition of the light - emitting film included npb ( n , n ′- bis ( naphthalen - 1 - yl )- n , n ′- bis ( phenyl )- benzidine ) and compound ( po - 01 - bp - dipig ) npb and compound ( po - 01 - bp - dipig ) ( the weight ratio between npb and compound ( po - 01 - bp - dipig ) was 95 : 5 ) were dissolved in chlorobenzene to prepare the light - emitting film . next , a tmpypb ( 1 , 3 , 5 - tri [( 3 - pyridyl )- phen - 3 - yl ] benzene ) layer ( with a thickness of 55 nm , serving as a hole - block / electron - transport layer ) was deposited on the light - emitting film . next , a lif layer ( with a thickness of 1 nm ) and an al layer ( with a thickness of 100 nm ) were subsequently deposited on the tmpypb film and packaged , obtaining the organic electroluminescent device ( 6 ). the structure of the organic electroluminescent device ( 6 ) is described in the following : ito ( 150 nm )/ pedot : pss ( 45 nm )/ npb : compound ( po - 01 - bp - dipig ) ( 30 nm )/ tmpypb ( 55 nm )/ lif ( 1 nm )/ a1 ( 100 nm ) the optical properties including brightness ( cd / m 2 ), current efficiency ( cd / a ), power efficiency ( 1 m / w ), emission wavelength ( nm ), and color coordinates ( x , y ) of the organic electroluminescent device ( 6 ) were measured and the results are described in table 2 . a glass substrate with a patterned indium tin oxide ( ito ) film of 150 nm was provided and then washed with a neutral cleaning agent , acetone , and ethanol with ultrasonic agitation . after drying the substrate with a nitrogen flow , the substrate was subjected to a uv / ozone treatment for 30 minutes . next , pedot ( poly ( 3 , 4 )- ethylendioxythiophen ) and pss ( e - polystyrenesulfonate ) were selected to coat on the ito film by a spin coating process ( with a rotation rate of 2 , 000 rpm ) to form a pedot : pss film ( with a thickness of 45 nm , serving as a hole injection layer ). after heating to 130 ° c . for 10 min , a tapc ( di -[ 4 -( n , n - ditolyl - amino )- phenyl ] cyclohexane ) layer ( with a thickness of 35 nm ), a tcta ( 4 , 4 ′, 4 ″- tris ( carbazol - 9 - yl ) triphenylamine ) layer doped with commercial compound ( ir ( phq ) 2 acac ) ( bis ( 2 - phenylquinoline )( acetylacetonate ) iridium ( iii )) ( the ratio between tcta and compound ( ir ( phq ) 2 acac ) was 100 : 6 , with a thickness of 10 nm ), a tmpypb ( 1 , 3 , 5 - tri [( 3 - pyridyl )- phen - 3 - yl ] benzene ) layer ( with a thickness of 42 nm ), a lif layer ( with a thickness of 0 . 5 nm ), and an al layer ( with a thickness of 120 nm ) were subsequently deposited on the ito film under 10 − 6 torr and packaged , obtaining the organic electroluminescent device ( 7 ). the structure of the organic electroluminescent device ( 7 ) is described in the following : ito ( 150 nm )/ tapc ( 35 nm )/ tcta : compound ( ir ( phq ) 2 acac ) ( 6 %, 10 nm )/ tmpypb ( 42 nm )/ lif ( 0 . 5 nm )/ al ( 120 nm ) the optical properties including brightness ( cd / m 2 ), current efficiency ( cd / a ), power efficiency ( 1 m / w ), emission wavelength ( nm ), and color coordinates ( x , y ) of the organic electroluminescent device ( 7 ) were measured and the results are described in table 2 . a glass substrate with a patterned indium tin oxide ( ito ) film of 150 nm was provided and then washed with a neutral cleaning agent , acetone , and ethanol with ultrasonic agitation . after drying the substrate with a nitrogen flow , the substrate was subjected to a uv / ozone treatment for 30 minutes . next , pedot ( poly ( 3 , 4 )- ethylendioxythiophen ) and pss ( e - polystyrenesulfonate ) were selected to coat on the ito film by a spin coating process ( with a rotation rate of 2 , 000 rpm ) to form a pedot : pss film ( with a thickness of 45 nm , serving as a hole injection layer ). after heating to 130 ° c . for 10 min , a light - emitting film ( with a thickness of 30 nm ) was formed on the pedot : pss film by a spin coating process . the composition of the light - emitting film included tcta ( 4 , 4 ′, 4 ″- tris ( carbazol - 9 - yl ) triphenylamine ) and compound ( ir ( phq ) 2 acac ) ( bis ( 2 - phenylquinoline )( acetylacetonate ) iridium ( iii )). tcta and compound ( ir ( phq ) 2 acac ) ( the weight ratio between tcta and compound ( ir ( phq ) 2 acac ) was 95 : 5 ) were dissolved in chlorobenzene to prepare the light - emitting film . next , a tmpypb ( 1 , 3 , 5 - tri [( 3 - pyridyl )- phen - 3 - yl ] benzene ) layer ( with a thickness of 45 nm , serving as a hole - block / electron - transport layer ) was deposited on the light - emitting film . next , a lif layer ( with a thickness of 1 nm ) and an al layer ( with a thickness of 100 nm ) were subsequently deposited on the tmpypb film and packaged , obtaining the organic electroluminescent device ( 8 ). the structure of the organic electroluminescent device ( 8 ) is described in the following : ito ( 150 nm )/ pedot : pss ( 45 nm )/ tcta : compound ( ir ( phq ) 2 acac ) ( 30 nm )/ tmpypb ( 45 nm )/ lif ( 1 nm )/ a1 ( 100 nm ) the optical properties including brightness ( cd / m 2 ), current efficiency ( cd / a ), power efficiency ( 1 m / w ), emission wavelength ( nm ), and color coordinates ( x , y ) of the organic electroluminescent device ( 8 ) were measured and the results are described in table 2 . it will be apparent to those skilled in the art that various modifications and variations can be made to the disclosed embodiments . it is intended that the specification and examples be considered as exemplary only , with the true scope of the disclosure being indicated by the following claims and their equivalents .