This work developed a three-dimensional, multiphysics, and transient model to investigate transient supercooling of TECs (thermoelectric coolers). The model coupled the heat and electricity conductions and considered all thermoelectric effects. The model was well validated by dynamic test data for a TEC (Thermoelectric cooler) start-up process and was compared with the previous heat conduction model. The comparison confirmed that the multiphysics model has a more superior performance for predicting the key evaluation parameters of the transient supercooling. Then the model was used to investigate various current pulses (t(0), t(1/2), t(2), t(3), t(4), and t(5)) to search for the optimal shape. The results showed that the optimal shape is only determined by the time to reach the minimum cold end temperature (t(min)) and the pulse, width (tau). For the pulses with t(min) < tau, a higher power pulse provides a lower cold end temperature, for the pulses with tmin = tau, however, the trend is opposite. The present results reasonably explain the divergence for the optimal pulse shape reported by the previous studies. (C) 2015 Elsevier Ltd. All rights reserved.