Investigation and modeling of photocurrent collection process in multiple quantum well solar cells

Abstract

Solar cells employing quantum wells can enhance the light absorption but suffer from the difficulty in photogenerated carrier extraction. Here, we analyzed the spectral response and the photocarrier collection mechanism of p-i-n multiple quantum well (MQW) solar cells using the effective-mobility model. Both the simulation and experiment results imply that the spatial profiles of electron and hole densities in MQWs play an important role in the carrier collection process. By considering the recombination increment under illumination, our findings suggest that the concept of the majority/minority carriers is important even in the intrinsic region: photogenerated electrons and holes only experience significant recombination when passing through the hole-rich and electron-rich regions, respectively. This can accurately explain the photocurrent behavior in cells with high background doping, background illumination, and different MQW positions. Based on the experimental findings, we derived analytical formulae for carrier collection efficiency, which directly show the impact of each cell parameter and can be used for the systematic cell design. . For w = 5 nm, the escape rate is boosted by less than 10% under E = 10 kV/cm compared to that under flat-band.

Generalized Reciprocity Relations in Solar Cells with Voltage-Dependent Carrier Collection: Application to p - i - n Junction Devices

“…and (22) (23) where ∆εF,D(rg, V) is the quasi-fermi level splitting at the position rg under dark condition for the applied voltage V. By following the similar derivation in Eqs. (15) (24) we obtain an interesting relation between the photocurrent of a device with illumination [ Fig (28) for V ≠ 0, which violates the main assumption = (sc) n,V n L L in the derivation of the original theorem [12][13][14][15][16][17]. This The carrier-transport reciprocity is confirmed by the 1D simulation of the p-i-n device described in Table I.…”

“…the electron-rich region (Vn>p in Fig. 2), and the region that p>n, i.e. the hole-rich region (Vp>n) [28]. (Therefore, strictly speaking, the word "depletion region"…”

“…For the photogeneration in Vp>n, the electron photocurrent density Jph,n and the electron density increment ∆n due to illumination are related by [28] . n q n µ = ∆ ph ,n E J (33) The similar relation of the hole photocurrent density Jph,p and the hole density increment ∆p for the photogeneration in Vn>p can also be obtained.…”

“…For the photogeneration in Vp>n, the electron photocurrent density Jph,n and the electron density increment ∆n due to illumination are related by [28] .…”

Numerical Modeling of the Electronic and Electrical Characteristics of InGaN/GaN-MQW Solar Cells

“…In fact, the increase in temperature will decrease the probability of recombination of the photo-generated carriers; this effect will cause a limitation of the performance of the InGaN/GaN solar cell. To enhance the recombination of photogenerated carriers in MQW, and consequently, to improve the solar cell performance, increasing the indium fraction and the number of wells is a good solution [39].…”