Impact of implementing the Meyer-Neldel behavior of carrier emission pre-factors in solar cell and optical detector modeling

Abstract

Articles you may be interested in A study of quantum well solar cell structures with bound-to-continuum transitions for reduced carrier recombination Appl. Phys. Lett. 102, 213903 (2013) The Meyer-Neldel behavior reported for the emission probabilities of electrons and holes was included in our code, replacing the gap state capture cross sections of the Shockley-Read-Hall formalisms with capture cross sections containing an exponential function of the trap energy depth. The Meyer-Neldel energies for electrons and holes are the slopes of these exponentials. Our results indicate that emission probabilities of neutral states no deeper than approximately 0.45 eV and 0.37 eV from the conduction and valence band edges, respectively, can show a Meyer-Neldel behavior only, while on the other hand, its implementation in deeper gap states makes the replication of experimental J-V curves of p-i-n solar cells and detectors impossible. The Meyer-Neldel behavior can be included in all neutral capture cross sections of acceptor-like tail states without affecting the J-V characteristics, while it cannot be included in all capture cross sections of neutral donor-like tail states and/or defect states without predicting device performances below the experimental figures, that become even lower when it is also included in charged capture cross sections. The implementation of the anti Meyer-Neldel behavior at tail states gives rise to slightly better and reasonable device performances. V C 2015 AIP Publishing LLC.

Further insight on recombination losses in the intrinsic layer of a-Si:H solar cells using computer modeling tools

“…In previous contributions, 13,14 the J-V curves of a-Si:H based devices were analyzed with D-AMPS under dark and illuminated conditions. Our parameters were calibrated by fitting experimental J-V characteristic curves of p-i-n junctions with intrinsic layer thicknesses of 200, 400, and 600 nm.…”

“…4 Experimental dark and light J-V curves of the a-Si:H p-i-n devices and their corresponding fittings can be found elsewhere. 13 The electrical parameters obtained from our fittings are listed in the second column of Table I. In our simulations, doping densities and Gaussian peak positions were adjusted to reproduce the experimental activation energies of each device layer.…”

“…Undiluted Naturally, electrical parameters used by different groups working on a-Si:H solar cell modeling show some spread. [11][12][13][14][16][17][18][19][20][21][22] However, the electrical parameters of Liang and Schiff 4,15,23 have two unusual features: a considerably higher density of states at mobility edges (G AO ¼ 1.6 Â 10 22 cm À3 and G DO ¼ 6 Â 10 21 cm À3 ) with narrower tails (E A ¼ 20 meV and E D ¼ 40 meV) and poor free carrier mobilities (l N ¼ 2 cm 2 V À1 s À1 and l P ¼ 0.3 cm 2 V À1 s À1 ). These unusual parameters have a significant impact on the predicted J-V characteristics.…”

“…The lowering of E D from 48 meV to 40 meV significantly impacts the predicted solar cell performance, being E D usually assumed between 44 and 50 meV in the literature. 13,14,18,19,23 Table IV shows the solar cell performances predicted with D-AMPS when our electrical parameters, obtained from fittings of J-V curves of a-Si:H p-i-n devices grown at Delft University, were replaced one at a time by the values proposed by Liang et al 4 Although we performed simulations for solar cells with different thicknesses of the intrinsic layer, only results for the 893-nm-thick layer are presented in Table IV, as in Ref. 4.…”

“…The most significant contributions to recombination losses at the intrinsic layer, that determine to a great extend V OC , take place at donor-like tail and defect states. 13 The contribution of acceptor-like tail states is not significant due to the steeper conduction tail slope. 13 Using the 1% criterion for the solar cell efficiency and assuming E A ¼ 30 meV (second column of Table I), TABLE IV.…”