{"action":"opened","issue":{"url":"https://api.github.com/repos/NREL/ssc/issues/155","repository_url":"https://api.github.com/repos/NREL/ssc","labels_url":"https://api.github.com/repos/NREL/ssc/issues/155/labels{/name}","comments_url":"https://api.github.com/repos/NREL/ssc/issues/155/comments","events_url":"https://api.github.com/repos/NREL/ssc/issues/155/events","html_url":"https://github.com/NREL/ssc/issues/155","id":320913842,"number":155,"title":"thin film recombination current loss term","user":{"login":"mikofski","id":1385621,"avatar_url":"https://avatars1.githubusercontent.com/u/1385621?v=4","gravatar_id":"","url":"https://api.github.com/users/mikofski","html_url":"https://github.com/mikofski","followers_url":"https://api.github.com/users/mikofski/followers","following_url":"https://api.github.com/users/mikofski/following{/other_user}","gists_url":"https://api.github.com/users/mikofski/gists{/gist_id}","starred_url":"https://api.github.com/users/mikofski/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/mikofski/subscriptions","organizations_url":"https://api.github.com/users/mikofski/orgs","repos_url":"https://api.github.com/users/mikofski/repos","events_url":"https://api.github.com/users/mikofski/events{/privacy}","received_events_url":"https://api.github.com/users/mikofski/received_events","type":"User","site_admin":false},"labels":[],"state":"open","locked":false,"assignee":null,"assignees":[],"milestone":null,"comments":0,"created_at":"2018-05-07T18:49:25Z","updated_at":"2018-05-07T18:49:25Z","closed_at":null,"author_association":"NONE","body":"According to [PVPMC \"modeling steps\"](https://pvpmc.sandia.gov/modeling-steps/2-dc-module-iv/diode-equivalent-circuit-models/pvsyst-module-model/) and [PVSyst help files](http://files.pvsyst.com/help/thinfilm_recombinationloss.htm) there is a deviation between the single-diode model (SDM) and measurements of current for thin-film devices as voltage approaches open-circuit. A correlation was proposed by J. Merten which is discussed in [Mermoud, Lejeune [2010] **Performance Assessment of a Simulation Model for PV Modules of Any Available Technology** _EUPVSEC-25_](https://github.com/NREL/ssc/files/1981028/Mermoud.Lejeune.-.2010.-.Performance.Assessment.of.a.Simulation.Model.for.Pv.Modules.of.Any.Available.Technology.pdf). See also [**Improved equivalent circuit and analytical modle for a:Si solar cells and modules** J Merten, _et al._ [1998] _IEEE Trans on Elec Dev_](https://doi.org/10.1109/16.658676).\r\n\r\nThe basic form of the equation is:\r\n\r\n    I_rec = I_L * d2_mu_tau / (V_bi - V_diode)\r\n\r\nwhere:\r\n\r\n* `d2_mu_tau` is the ratio of the square of the thickness of the intrinsic thin flim layer (d<sub><i>i</i></sub><sup>2</sup>), and the mean effective diffusion length (&mu;&tau;<sub><i>eff</i></sub>), typically given as 1.4V\r\n* `V_bi` is the \"built-in\" voltage of the intrinsic layer, typically given as 0.9V for a:Si, but in practice is varied to minimize difference between measured and predicted  Voc (or Pmp).\r\n* `V_diode = Vcell + Icell * Rseries`  is the junction or \"diode\" voltage of the SDM\r\n\r\nIn practice combine the thin film recombination current `I_rec` using Kirchhoff's law\r\n\r\n    I_cell = I_L - I_diode - I_shunt - I_rec"}}
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