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Polarization of CdTe radiation detectors in the dark was studied theoretically by taking into account a wide set of detector characteristics relevant to the polarization. Drift-diffusion and Poisson's equations were solved numerically in one dimension in time-resolved regime, where the characteristic time is determined by the charging of detector bulk. Shockley-Read-Hall model describes the trapping/detrapping of free carriers. Both diode-like (In,Al)/CdTe/Pt and symmetrical (In,Al,Pt)/CdTe/(In,Al,Pt) detectors were considered. We showed how the space charge is formed in time after detector biasing and a `dead layer' appears in the detector when the accumulated charge screens the bias. Numerical results were compared with the Conventional model of charge accumulation. The influence of temperature on polarization was analyzed and the polarization is correlated with current transient. The approach can be conveniently used to find principal properties of trap levels and contacts in semiconductor radiation detectors.