Photovoltage decay processes in Cu(In, Ga)Se<inf>2</inf> solar cells studied by photo-assisted Kelvin probe force microscopy

Abstract

The temporally-averaged photovoltages were measured on Cu(In,Ga)Se 2 [CIGS] solar cells under the intermittent light excitation by photo-assisted Kelvin probe force microscopy to evaluated a time constant  for photovoltage decay and a contribution ratio r of fast carrier recombination process in the entire recombination processes. The results indicate that the sample with higher Ga content exhibited longer  and larger r, from which we have investigated the influences of both the carrier transport across the potential barrier and the carrier separation around the grain boundary on the entire photo-carrier recombination processes.

Multi-pulse modulation method in photothermal atomic force microscopy for variable frequency modulation of incident light

“…2(b) and their period (= f 1 p ) was varied, which is similar to the way used for photovoltage decay measurements in photo-assisted Kelvin probe force microscopy. [16][17][18][19][20] The PT signal was extracted from an output of PLL by the lock-in amplifier synchronized at a frequency f s , which should represent an averaged phase change over the light illumination duration, corresponding to a mean value of thermal expansion. If we change f s in the SW method shown in Fig.…”

Electrostatic force and Kelvin probe force microscopies on Cu(In,Ga)Se<inf>2</inf> solar cells

“…Most of the CIGS materials used in solar cells have a microcrystalline structure that consists of many small grains, and therefore it is important to investigate photo-carrier dynamics and their recombination properties around grain boundaries (GBs) in order to improve the solar cell performances. For such purposes, microscopic investigations by scanning probe microscopies are very informative, and several works have been reported [3]- [10]. In this study, we performed electrostatic force microscopy (EFM) and Kelvin probe force microscopy (KFM) on the CIGS solar 2.…”