The power conversion efficiency (PCE) of a 54-mu m-thick InGaP/InGaAs/Ge triple-junction (3-J) solar cell transferred on a flexible polyimide (PI) substrate (transferred thinned solar cell) was investigated at -150 degrees C-+150 degrees C under the AM0 condition. The transferred thinned InGaP/InGaAs/Ge 3-J solar cell was fabricated by grinding and polishing a 190-mu m-thick commercial InGaP/InGaAs/Ge 3-J solar cell (pristine thick solar cell). The temperature coefficients for V-oc, J(sc), PCE, and P-max in the pristine thick solar cell were -4.95 mV/degrees C, 11.75 mu A/cm(2)/degrees C, -0.04%/degrees C, and -16.56 mu W/degrees C, respectively, in the temperature range of -150 degrees C to +150 degrees C. In the transferred thinned solar cell, the temperature coefficients for V-oc, J(sc), PCE, and P-max were -0.97 mV/degrees C, 2.53 mu A/cm(2)/degrees C, -0.01%/degrees C, and -2.16 mu W/degrees C in the temperature range of -150 degrees C to +150 degrees C. In the temperature range of 0 degrees C-150 degrees C for the transferred thinned solar cell, the temperature coefficients for V-oc, J(sc), PCE, and P-max were -4.53 mV/degrees C, 9.22 mu A/cm(2)/(C degrees), -0.04%/degrees C, and -16.81 mu W/degrees C, respectively. The temperature-dependent external quantum efficiency (EQE) of each subcell in a pristine thick and transferred thinned solar cell explained the result that the absolute values of the temperature coefficients in the transferred thinned solar cell are lower than those in the pristine thick solar cell in the -150 degrees C-0 degrees C temperature range. A structural deformation was observed in the transferred thinned solar cell and it affected the temperature-dependent photovoltaic properties of the transferred thinned solar cell. The deformation also changed the photovoltaic properties of the transferred thinned solar cell measured under vacuum pressures for a high-altitude environmental simulation. (C) 2016 Elsevier B. V. All rights reserved.