NOVELTY - Use of pyrrolo (3,2-B) pyrrole-2,5-dione (I) or formulation comprising pyrrolo (3,2-B) pyrrole-2,5-dione as organic semiconductor, is claimed.    USE - Use of pyrrolo pyrrole-2,5-dione or its formulation as organic semiconductor, charge transport material, semiconducting material, electroconductive material or photoconducting material in optical, electrooptical or electronic component or device e.g. organic field effect transistors (OFET), thin film transistors (TFT), integrated circuits (IC), logic circuits, capacitors, radio frequency identification (RFID) tags, organic light emitting diodes (OLED), organic light emitting transistors (OLET), flat panel displays, backlights of displays, organic photovoltaic devices (OPV), solar cells, laser diodes, photoconductors, photodetectors, electrophotographic devices, electrophotographic recording devices, organic memory devices, sensor devices, charge injection layers, charge transport layers or interlayers in polymer light emitting diodes (PLEDs), organic plasmon-emitting diodes (OPEDs), Schottky diodes, planarizing layers, antistatic films, polymer electrolyte membranes (PEM), conducting substrates, conducting patterns, electrode materials in batteries, alignment layers, biosensors, biochips, security markings, security devices, and components or devices for detecting and discriminating DNA sequences (all claimed).    ADVANTAGE - The formulation has high mobility and uniformly coated on large area. The organic field effect transistor formed using the formulation has favorable stability.    DETAILED DESCRIPTION - Use of pyrrolo (3,2-B) pyrrole-2,5-dione of formula (I) or formulation comprising pyrrole (3,2-B) pyrrole-2,5-dione as organic semiconductor, is claimed.    X1,X2=O or S;    Ar1-Ar6=-CY1=CY2-, -CC-, or 5-30 op membered aryl or heteroaryl optionally substituted by R1 or R3, different from pyrrolo(3,2-b)pyrrole-2,5-dione;    R1,R2=H, -C(O)R0, -O-C(O)R0, -CF3, P-Sp-, or silyl, carbyl or 1-40C hydrocarbyl (all optionally substituted and optionally comprising one or more hetero atoms, and in which one or more C atoms are optionally replaced by hetero atom);    R3,R4=F, Br, Cl, -CN, -NC, -NCO, -NCS, -OCN, -SCN, -C(O)NR0R00, -C(O)X0, -C(O)R0, -C(O)OR0, -O-C(O)R0, -NH2, -NR0R00, -SH, -SR0, -SO3H, -SO2R0, -OH, -NO2, -CF3, -SF5, P-Sp-, or silyl, carbyl or hydrocarbyl (all optionally substituted and optionally comprising one or more hetero atoms, and in which one or more C atoms are optionally replaced by hetero atom);    R0,R00=H or optionally substituted 1-4C carbyl or hydrocarbyl;    P=polymerizable or crosslinkable group;    Sp=spacer group or single bond;    X0=halogen, preferably F, Cl or Br;    Y1,Y2=H, F, Cl or CN;and    a-f=0-3, at least one of a-c and at least one of d-f is different from 0.    An INDEPENDENT CLAIM is included for pyrrolo (3,2-B) pyrrole-2,5-dione (I).