講演情報
[21p-C601-11]Combined Charge Extraction by Linearly Increasing Voltage and Time-Resolved Microwave Conductivity to Reveal the Dynamic Charge Carrier Mobilities in Thin-Film Organic Solar Cells
〇(D)Shaoxian Li1, Ryosuke nishikubo1, Akinori Saeki1 (1.Osaka University)
キーワード：
organic solar cell、carrier transport dynamics、solar cell
Charge carrier mobility (μ) is conventionally regarded as a time-independent constant during charge transport, which often fails to account for the OSC performance. Recently, the μ in OSCs has been observed to be time-dependent during charge transport, decaying by as large as six orders in a wide timescale (~10–13–10–3 s). However, reports on separately measuring time-dependent electron mobility (μe) and hole mobility (μh) in OSCs at a timescale of 10–6–10–4 s (typical charge extraction time) are still rare. For this issue, we reported a combined CELIV-TRMC technique to measure the time-dependent mobility in OSCs, using simultaneous charge extraction by linearly increasing voltage (CELIV) and time-resolved microwave conductivity (TRMC) measurements. This method is purely experiment-based, applicable to thin films (~100 nm, identical to that of real-working OSC) and capable of measuring time-dependent μe and μh in a timescale of 10–6–10–4 s. We proposed a new CELIV injection profile, named slope-injection-restoration, for clear identifications of the injection current plateau, rendering more accurate determination of the charge densities. Based on the CELIV-TRMC transients, the applicant proposed a formula for time-dependent μe and μh. The results well matched the conventional time-averaged CELIV mobilities, proving their accuracy. Further, the time-dependent mobility ratio (mobility balance) in several NA and NFA OSCs was obtained, in a timescale of 30 μs. This study is the first to report purely experimental time-dependent mobility balance in thin-film BHJ OSCs within tens of microseconds. The new CELIV-TRMC technique offers a path toward comprehensive understandings of time-dependent mobility and its correlation with the performance of FA- and NFA-based OSCs.