Imbalanced charge mobility in oxygen treated polythiophene/fullerene based bulk heterojunction solar cells

Abstract

The effect of oxygen induced traps on charge mobility in bulk heterojunction solar cells using poly (3-hexylthiophene) (P3HT):1-(3-methoxycarbonyl)-propyl-1phenyl-(6, 6) methanofullerene (PCBM) blend have been studied using photoinduced charge extraction by linearly increasing voltage (PhotoCELIV) technique. The solar cells exposed to oxygen exhibit dual PhotoCELIV peaks, whereas the solar cell without oxygen treatment show single PhotoCELIV peak with the charge mobility of the order of 10-4 cm 2 /Vs. It is demonstrated that the oxygen treatment imbalance the charge mobility in the P3HT/PCBM photoactive layer, which affects the power conversion efficiency and lifetime of the solar cell. The single PhotoCELIV peak for the device without oxygen treatment indicates that the charge mobility is balanced, that causes the overlapping of electron and hole transients.

Direct Evaluation of Intrinsic Optoelectronic Performance of Organic Photovoltaic Cells with Minimizing Impurity and Degradation Effects

“…Therefore ϕ in the fl at region is close to but not equal to the unity, leading to the situation that ϕ Σ μ max represent the minimum Σ μ . An emphasis is given to that such a high minimum average mobility of 0.22 cm 2 V − 1 s − 1 was found even in the P3HT:PCBM = 1:1 fi lm, although the values of mobility in the order of 10 − 4 to 10 − 6 cm 2 V − 1 s − 1 have been reported in BHJ fi lms by SCLC [ 38 ] or photo-induced charge extraction by linearly increasing voltage (PhotoCELIV) [ 39 ] techniques. This suggests the considerable suppression of charge carrier mobility by disordered domain, grain boundary, interface barrier, and impurities in BHJ fi lm.…”

Bimolecular recombination coefficient calculation by in situ potentiometry in a bulk heterojunction organic photovoltaic material

“…These values are shown in Table I and are consistent with previous reports using photo-CELIV and SCL based methods. 10,[15][16][17] The carrier concentration and the bimolecular recombination coefficient are calculated using Eqs. (5) and (6).…”

Use of lateral structures to monitor and evaluate degradation of key photovoltaic parameters in an organic bulk heterojunction material

“…These values are consistent with previous reports using photo-CELIV and SCL based methods. 12,[24][25][26] Although a decrease in the recombination zone conductivity was observed over time, we attribute this to a significant decrease in mobility rather than a change in the recombination characteristics. The carrier concentration and recombination coefficient remain relatively constant over the course of the experiment, while both carrier mobilities decrease significantly.…”