We compare the dependencies of performance of bifacial and monofacial mini-modules on the impinging solar radiation intensity, spectrum and the ground albedo. Monofacial and bifacial mini-modules realized with n-type Si heterojunction solar cells were tested in outdoor conditions. Two different types of ground, with a low and high albedo, have been used. By studying the correlation between short circuit current and power at the maximum power point of the modules with the solar radiation intensity, spectrum and with the ground albedo, we provide understanding on the measured peculiar time evolution of the bifacial module performance along the daytime.