Crystal growth of Cu2ZnSnS4 solar cell absorber by chemical vapor transport with I2

► Cu2ZnSnS4 crystals were grown by the chemical vapour transport with I2. ► Two different I2 loads were employed to investigate the possible incongruent transport of the pentanary system. ► Microscopic and nanoscopic uniformity point to high quality homogeneous material. ► Longitudinally isothermal CVT treatments were attempted for the first time. ► We propose a simplistic mechanism of crystal growth and envisage the conditions for enlargement of crystals under isothermal CVT.