Microsecond photocapacitance transients observed using a charged microcantilever as a gated mechanical integrator.
Microsecond photocapacitance transients observed using a charged microcantilever as a gated mechanical integrator.
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DOI：
10.1126/sciadv.1602951
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发表时间：
2017-06
期刊：
影响因子：
13.6
通讯作者：
Marohn JA
中科院分区：
文献类型：
--
作者：
Dwyer RP;Nathan SR;Marohn JA
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A new way to measure the rate of light-induced charge generation in organic solar cell films with a nanometer-scale probe. How light is converted to electricity in blends of organic donor and acceptor molecules is an unsettled question, partly because the spatial heterogeneity present in these blends makes them challenging to characterize. Although scanned-probe measurements have provided crucially important microscopic insights into charge generation and transport in these blends, achieving the subnanosecond time resolution needed to directly observe the fate of photogenerated charges has proven difficult. We use a charged microcantilever as a gated mechanical integrator to record photocapacitance indirectly by measuring the accumulated change in cantilever phase as a function of the time delay between precisely synchronized voltage and light pulses. In contrast with previous time-resolved scanned-probe photocapacitance measurements, the time resolution of this method is set by the rise and fall time of the voltage and light pulses and not by the inverse detection bandwidth. We demonstrate in an organic donor-acceptor blend the ability of this indirect, “phase-kick” technique to record multiexponential photocapacitance transients on time scales ranging from 40 μs to 10 ms. The technique’s ability to measure subcycle, nanosecond charge dynamics is demonstrated by measuring the tens of nanosecond sample electrical charging time.