Study on dynamics of photoexcited charge injection and trapping in CdS quantum dots sensitized TiO2 nanowire array film electrodes

Abstract

The photoexcited electrons transfer dynamics of the CdS quantum dots (QDs) deposited in TiO2 nanowire array films are studied using surface photovoltage (SPV) and transient photovoltage (TPV) techniques. By comparing the SPV results with different thicknesses of QDs layers, we can separate the dynamic characteristics of photoexcited electrons injection and trapping. It is found that the TPV signals of photoexcited electrons trapped in the CdS QDs occur at timescales of about 2 × 10−8 s, which is faster than that of the photoexcited electrons injected from CdS into TiO2. More than 90 nm of the thickness of the CdS QDs layer will seriously affect the photoexcited electrons transfer and injection.

A structure of CdS/CuxS quantum dots sensitized solar cells

“…Other possibility such as interfacial trapping can be excluded here, as the decreased PL band width indicates the reduction of interfacial trapping state concentration if the Cu x S layer is present in QDs. 37,38 Moreover, the charge carrier dynamics and solar cell performance studies in the following part do confirm the improvement of the charge separation by Cu x S layer coating in our system.…”

Exploiting Electrical Transients to Quantify Charge Loss in Solar Cells

“…transient photocurrent (TPC) and photovoltage (TPV)) [30][31][32][33][34][35][36][37] enabled by optical excitation and electric detection provide an opportunity to study charge transport, recombination and even the hysteresis in a much wider time window. This technique has been widely applied for silicon, [38][39] sensitized, [40][41] quantum dot, 42 organic 43 and recent the perovskite solar cells. [30][31][32][33][34][35] A generic physics model and quantitative analysis method centered on the charge occupation of subgap tail states has been extended from sensitized to current perovskite solar cells.…”

Photophysical investigation of charge recombination in CdS/ZnO layers of CuIn(S,Se)2 solar cell

“…23,24 In the case of s 1 , the peak at 420 nm is three times higher than the peak at 380 nm, which proves that the faster component s 1 is dominated by recombination in the CdS layer. 18,26,27 Optical pump and optical probe measurements were obtained by pumping and probing with femtosecond laser pulses (100 fs, 1 kHz). Recombination in the CdS/ZnO layers reduces the photocurrent in the device.…”

“…25 The lower efficiency is because of the trapping (capture) and detrapping (emission) of carriers by the CdS and ZnO layers. 18,26,27 Optical pump and optical probe measurements were obtained by pumping and probing with femtosecond laser pulses (100 fs, 1 kHz). The fundamental and second harmonic wavelengths of the laser were chosen for the pump, and output from OPA (900 nm) was chosen as the probe.…”