We propose a novel technique of determining relationship between effective and bulk diffusion length of single-crystalline Si (c-Si) thin-film solar cells using two-dimensional device simulator. In addition, bulk diffusion length was obtained using the result of the simulation. Effective diffusion length was measured by LBIC method in order to presume bulk diffusion length of c-Si thin film. We obtained 6.7 mum for effective diffusion length of c-Si thin-film solar cell whose thickness was about 7 mum. We compared the result of measurement and simulation, bulk diffusion length of c-Si thin film prepared by CVD method was estimated more than 30 mum and recombination velocity was presumed < 10(4) cm/s for front surface and 10(3) cm/s for rear surface of the cell. (C) 2002 Elsevier Science B.V. All rights reserved.