X-ray detectors are made by growing CsPbI.sub.3 on a treated surface of a conductive layer. Growth is controlled by increasing solvent concentration in the atmosphere in which the growth occurs. Columnar crystals grown in a plurality of wells extend between conductive surfaces at least one of which is pixelated to produce a columnar detector array.

X-ray detectors are made by growing CsPbI.sub.3 on a treated surface of a conductive layer. Growth is controlled by increasing solvent concentration in the atmosphere in which the growth occurs. Columnar crystals grown in a plurality of wells extend between conductive surfaces at least one of which is pixelated to produce a columnar detector array.