Organic field effect transistors (OFET) have so far not achieved major commercial impact, despite their many attractive properties such as low-cost, low-temperature processing, and flexibility. In this talk, I will discuss recent work which addresses some of the shortcomings of the OFET. One key approach is to introduce controlled electrical doping into OFET structures (K. Walzer et al., Chem. Rev. 107, 1233 (2007)). We have recently shown (B. Lüssem et al., Nature Comm. 4, 2775 (2013)) that this allows for the first time the realization of organic inversion transistors. Furthermore, we have shown that doping significantly reduces bias stress, one of the major drawbacks of OFET (M.P. Hein et al., Appl. Phys. Lett. 104, 013507 (2914)). Finally, I will discuss vertical transistor structures which have very short channel length without micropatterning. These structues allow much higher current densities than the lateral OFET despite rather simple processing technology without high-resolution patterning (A. Fischer et al., Appl. Phys. Lett. 101, 213303 (2012)) . These devices are well suited to drive organic light emitting diodes (OLED), allowing all-organic flexible OLED displays.